1. Technical Field
The disclosure concerns a plasma-enhanced reactive ion etch (PERIE) process for a workpiece such as a semiconductor wafer.
2. Background Discussion
In conventional atomic layer etching, a PERIE process removes an overlying layer (e.g., silicon dioxide) formed on a base layer (e.g., Silicon). The removal is performed one atomic layer at a time, as follows: The top atomic layer is passivated by a exposing it to a passivating process gas for the amount of time required for just one atomic layer to react with the passivating process gas, leaving underlying atomic layers unchanged. The one atomic layer that has been thus passivated may be referred to as the passivated layer. Species from the passivating process gas are chemically bound with material in the passivated layer, altering its characteristics. The passivated layer is susceptible to etching by a particular etch species, while the underlying layers remain impervious to the particular etch species. Upon completion of the passivation of a single atomic layer, the passivation process gas is removed for example by purging the processing chamber. The passivated layer is then etched by introducing a different process gas containing the particular etch species. Upon completion of the etch operation, the chamber is again purged. The foregoing operations of passivation and etching, including the change or purging of process gases, are then repeated for the next atomic layer. The cycle is continued until all atomic layers have been removed. One problem with this conventional process is that the purging and changing of process gases is time consuming, and must be performed for each atomic layer. Given the large number of atomic layers within the thickness of a typical silicon dioxide layer, the entire process is very time-consuming.